Here’s an in-depth look at the decision from Gia Austin writing for the University of Denver Water Law Review. Click through and read the whole article. Here’s an excerpt:

The parties divided the litigation into three phases. With respect to Phase I, the only phase relevant for this case, the district court held that “the reserved rights doctrine applied to groundwater and that the United States reserved appurtenant groundwater when it established the Tribe’s reservation.” Subsequently, the district court certified its order for interlocutory appeal and the water agencies petitioned the Ninth Circuit Court of Appeals for permission to hear the appeal. The court, on de novo review, addressed the only issue on appeal: whether the Tribe had a federal reserved right to the groundwater underlying its reservation. In so doing, the court approached its analysis in three steps.

First, the court determined whether the United States impliedly reserved water when establishing the Agua Caliente Reservation. This question is two-pronged: (1) whether water is reserved if a reservation’s primary purpose anticipates water use; and (2) if so, whether the Agua Caliente Reservation’s primary purpose contemplated water use.

The court began its analysis by examining the Winters doctrine, and found that it established that “federal reserved water rights are directly applicable ‘to Indian reservations and other federal enclaves, encompassing water rights in navigable and nonnavigable streams.’” However, the Winters doctrine is limited to certain situations; it reserves water necessary to accomplish the purported means of the reservation and reserves water if it is appurtenant to the withdrawn land. Following that understanding, the court differentiated the parties’ and the district court’s application of the Winters doctrine that specifically addressed whether the Tribe’s reserved right extended to groundwater from the more overarching issue concerning whether the mere existence of a federal reserved right depended on the Agua Caliente Reservation maintaining an implicit right to use water.

The court then evaluated the first prong when addressing the Tribe’s implied reserved right to water. The court invoked United States v. New Mexico and reasoned, “the federal purpose for which land was reserved is the driving force behind the reserved rights doctrine.” Further, that the New Mexico Court patterned a consistent conclusion whenever the reserved water rights doctrine is raised—an insufficient water supply defeats the purposes of the reservation. Therefore, the court adopted New Mexico’s holding that water is reserved when the reservation’s primary purpose foresees water use. The court then evaluated the second prong, whether the Tribe’s primary purpose contemplated water use. To answer this question, the court synthesized the Executive Orders establishing the Agua Caliente Reservation and Supreme Court precedent to conclude that “the primary purpose underlying the establishment of the reservation was to create a home for the Tribe, and water was necessarily implicated in that purpose.” Therefore, the United States impliedly reserved water for the Tribe.

Second, the court addressed whether the Tribe’s implied reserved water right extended to the Agua Caliente Reservation’s underlying groundwater. The court reiterated the Winters doctrine requirements and determined that although the Tribe met the first requirement that the reservation’s purported means necessitated water use, the second requirement that unappropriated water must be appurtenant to the reservation remained. To find a resolution, the court reasoned that appurtenance is not limited to surface water and extrapolated from Supreme Court precedent that the United States can protect groundwater and, along that vein, impliedly reserved water may include appurtenant groundwater. Further, the court considered the Tribe’s reliance on groundwater when reasoning that the minimal surface water availability conditions the Tribe’s survival on groundwater access. From this line of reasoning, the court clarified that the Winters doctrine purported to provide sustainable livelihoods to Tribes inhabiting reservations in arid areas, like the Agua Caliente Reservation, and included access to both appurtenant surface water and groundwater. Therefore, the Tribe’s implied reserved water right included groundwater.

Third, the court addressed whether the above two holdings withstood the water agencies’ arguments that: (1) the Tribe received water pursuant to California’s correlative rights doctrine; (2) the Tribe did not need a federal reserved right to groundwater in light of its allotted surface water from the Whitewater River Decree; and (3) the Tribe never drilled for groundwater on its reservation. The court rejected each in turn. First, federal water rights, such as the implied federal reserved water right, preempt state water rights. Second, New Mexico did not inquire into the current necessity of water, it focused on whether the reservation’s inception purported such a necessity. Third, lacking historical access to groundwater on the reservation did not foreclose the Tribe’s current access to groundwater. Therefore, compounded with the federal primacy of reserved water rights, the Tribe’s implied federal water right to groundwater remained intact.

Accordingly, the court affirmed the district court holding that the United States impliedly reserved appurtenant groundwater when creating the Agua Caliente Reservation.